Nowadays, flat panel displays such as LCDs are widely applied to consumer electronic products such as mobile phones, laptop computers, desktop presenting means, television sets, etc. With the features of high resolution, compact size, and portability, etc., the applications of flat panel displays are diverse. Consequently, flat panel displays have been replacing conventional CRT displays and become a mainstream of display devices. For portable devices, power consumption is always an issue. Therefore, it is preferred to minimize power consumption of flat panel displays or make use of energy.